The present invention relates to a pump means, and more particularly to an eccentric vane pump to be mounted on an alternating current generator for an automobile, etc.
In general, this kind of eccentric vane pump has a construction as shown in FIGS. 1 to 3 of the attached drawings. In the drawings the reference numeral 1 designates an end frame or bracket of an alternating current generator for an automobile, not shown, 2 a shaft rotatively supported in end frame 1 by means of a bearing 3 and adapted to be driven by the alternating current generator, 2a a splined portion formed on shaft 2 at its free end portion, and 4 a rotor fixedly secured to shaft 2 through a spline coupling with splined portion 2a of shaft 2. Rotor 4 has a number (four in the instant example) of radial slots at equi-angular intervals, each slidably receiving a radial vane 5 therein. A housing 6 has a cylindrical inner peripheral surface the center of which is eccentric to the centers of shaft 2 and rotor 4. An annual disc 7 closes the open end of housing 6 to form a working chamber 8 of the pump in cooperation with shaft 2. A seal means 9 hermetically seals housing 6 relative to disc 7, and an oil seal means 10 is secured to disc 7 at its inner periphery with the inner periphery thereof be in contact with shaft 2 to hermetically seal working chamber 8 relative to the outside. Housing 6 and disc 7 are integrally secured to end frame 1 by means of bolts 11. An inlet port 12, and outlet port 13, and a lubrication orifice 14 are respectively provided in housing 6, inlet port 12, outlet port 13 and lubrication orifice 14 being adapted to be connected to a vacuum tank, an oil pan, and a lubricating pump, respectively, not shown. A protection cap 15 is mounted on splined portion 2a of shaft 2 when the rotor 4 is not mounted thereon for a reason to be explained later.
In operation, upon rotation of shaft 2 in the direction shown by the arrow in FIG. 2, radial vanes 5 slidably disposed within the slots formed in rotor 4 are urged radially outwards owing to the centrifugal force applied thereto by the rotating rotor 4 so as to have their outer end surfaces slide on the inner peripheral surface of housing 6 so that they perform a pump action to suck air from the vacuum tank through inlet port 12 and discharge it through outlet port 13. The lubricant oil fed into housing 6 through lubrication orifice 14 lubricates the relatively shifting surfaces of vanes 5 and the slots formed in rotor 4 and is discharged through outlet port 13 entrained in the discharged air.
In a conventional eccentric vane pump having the construction and operation as described above, since the outer diameter of splined portion 2a of shaft 2 and the inner diameter of the shaft engaging portion of oil seal means 10 formed at its inner periphery are identical, in order that oil seal means 10 be prevented from being injured by splined portion 2a of shaft 2 at the time of assembly of end frame 1 and disc 7 on which oil seal means 10 in mounted at its outer periphery, splined portion 2a of shaft 2 is required to be covered by protection cap 15 as shown in FIG. 3. In addition, owing to this requirement, since it is necessary for rotor 4 and housing 6 to be mounted on shaft 2 after disc 7 on which oil seal means 10 is mounted has been passed over shaft 2, housing 6 and disc 7 cannot be previously assembled as a pump proper secured together by means of pins or the like, so that the simplification of the assembly process is not possible.
In order to obviate this disadvantage, a further example of a conventional vane pump of this type has already been proposed. In this example, as shown in FIG. 4, there is provided a difference in outer diameters between the splined portion 16a of a shaft 16 and the shaft engaging portion of oil seal means 10 so that protection cap 15 as shown in FIG. 3 is not necessary at the time of assembly since there is no contact at the time of assembly. However, in this case, it is required that either the outer diameter of splined portion 16a of shaft 16 be made smaller than that of the conventional vane type pump as shown in FIGS. 1 to 3, or the outer diameter of the shaft engaging portion of oil seal means 10 be made larger than the conventional one. Therefore, there is caused such other drawbacks that the durability of splined portion 16a is reduced, or, since the dimension of bearing 3 becomes smaller as the outer diameter of the shaft engaging portion of oil seal means 10 becomes larger, the durability of bearing 3 becomes less, etc.